In The Case of the Poisoned Crops, Dr Frankl was a chemist and doctor who worked with General de Groot at the experimental station at Klookerstein in North Central Africa developing methods for dealing with locust swarms. Frankl had made a special study of the migration of the swarms. De Groot was later found to have been using drums of stolen "Vegicide" to poison crops. Frankl's name only cropped up during Air Commodore Raymond's briefing at the beginning. Biggles did not meet Frankl at Klookerstein, or if he was there, he did not introduce himself. Frankl's ultimate fate was not mentioned in the story.